Reaching and self-leveling loader



Sept. 26, 1961 w. E. ALBERT 3,001,654

REACHING AND SELF-LEVELING LOADER Filed Aug. 30, 1957 v a Sheets-Sheet 1 VALVES L3 WITH LOEK POJDTIDN A Hili VI f.. I INVENTOR.

W WM! 4/ 2 i P 1961 w. E. ALBERT 3,001,654

REACHING AND SELF-LEVELING LOADER Filed Aug. 30, 1957 3 Sheets-Sheet 2 IN VEN TOR.

p 1961 w. E. ALBERT 3,001,654

REACHING AND SELF-LEVELING LOADER Filed Aug. 30, 1957 3 Sheets-Sheet 3 IN VEN TOR.

Patented Sept. 26, 1961 3 001 654 REACHING AND SELl -LEVELING LOADER William E. Albert, Bensenville, Ill., assignor to Pettiboue Mulliken Corporation, a corporation of Delaware Filed Aug. 30, 1957, Ser. No. 681,306 2 Claims. (Cl. 214-140) Loaders built under Le Tendresse Patent Number 2,788,139 have proved that the reaching feature which is the subject of that patent is highly desirable. According to that patent, the simplicity of a pivoted boom for raising the load carrying forks or the like is combined with a linkage which permits a reaching action. According to this reaching action, a hydraulic cylinder provided for the reaching purpose is actuated to thrust the boom forwardly while maintaining it at a relatively constant level. During this reaching action, the main hydraulic cylinder which lifts the boom is in locked condition, the hydraulic lines to it being closed by their controlling valve. It is important to be able to attain this reaching action while the boom-lifting cylinder is in locked condition for two reasons. One is case of operating. Manipulation of valves for controlling two different moving cylinders would be somewhat difficult, especially While one hand is otherwise occupied, as in steering. A still more important reason is the fact that unless two different sources of hydraulic pressure were provided, any attempt to connect the source simultaneously to both the reaching cylinder and the lifting cylinder would be unsatisfactory because of two different cylinder pressures. The high pressure cylinder would tend to force its fluid into the cylinder of lower pressure, perhaps letting the load drop unintentionally.

According to the present invention, the advantages of reaching action are combined with a self-leveling linkage, so that as the boom is raised and lowered the load-carrying device will retain its pre-set angularity with respect to the ground. This is particularly important because of the fact that with a single source of hydraulic power, it is not practical to operate the leveling valve while the boom is being raised, or while the reaching action is in operation, for the reasons just discussed.

With the present invention it is possible, for example, to lower the boom in retracted position, set the fork at horizontal position, thrust the boom forwardly under -a stack of lumber, raise the boom, retract the boom for greater stability during transport, again cause the boom to reach, as may be required for depositing the load, all the while keeping the stack horizontally disposed so it will not slide in the stack.

Additional objects and advantages will be apparent from the following description and from the drawings.

Designation of figures FIGURES l to 4 are side views of the apparatus chosen for illustration of this invention showing four different positions of the boom, namely, low and reaching, high and retracted, high and reaching, and low and retracted.

FIGURE 5 is a front view of the apparatus approximately as shown in FIGURE 3, except that the fork is tilted to the horizontal position, and much detail has been omitted for clarity.

Background description Although the following disclosure offered for public dissemination is detailed to ensure adequacy and aid understanding, the claims at the end hereof are intended to meet the requirement of pointing out the parts, improvements, or combinations in which the inventive concepts are found.

The illustrated form of the invention includes or is applied to a vehicle frame or chassis 11 which runs on wheels 12.

A boom 13 carries a load handling unit or assembly 14 at its front end and at its rear end is pivoted to an upstanding link 16. Comparing FIGURES l and 3 it is seen that without movement of link 16, boom 13 can be raised and lowered. This is accomplished by a hydraulic jack or cylinder assembly 17. Comparing FIGURES 1 and 4, it is seen that without raising or lowering boom 13, link 16 may be pivoted flom the FIGURE 1 position to the FIGURE 4 position to retract the boom 13. Likewise link 16 may be moved in the opposite direction to advance the boom or reach. The reaching and retracting movements of link 16 are powered by a hydraulic jack or cylinder assembly 19. Commonly such cylinder assemblies, which include a piston, are just called cylinders.

It will be observed that the lifting jack or hydraulic cylinder 17 is generally parallel to the link 16. More specifically it will be observed that the pivotal axes 21 and 22 for the jack lie along a line fairly close to the line on which lie pivotal axes 23 and 24 for link 16. The resuit is that when link 16 is swung for a reaching or retracting action, there is relatively little change in the angularity of boom 13 with respect, to the ground or the frame 11. Accordingly the fork 25 or other load carrying the device remains at a nearly constant height during a reaching or retracting action. The fact that cylinder 19 (with piston) is sometimes longer than other times prevents attaining perfection in this.

Many of the parts so far described are in fact found in pairs. For example, as seen in FIGURE 5, there are two of the hydraulic lifting cylinders 17, and two of the reaching cylinders 19. In similar manner, some of the parts extend approximately the full width of the spacing between the pairs of cylinders 19. For example, link 16 is a sturdy full-Width casting as seen in FIGURE 5. Boom 13 is made up mainly of two spaced bars. These are mostly hidden in FIGURE 5 but portions thereof shown are both numbered 13.

Forward location of boom In La Tendresse Patent 2,788,139, the boom extends the full length of the vehicle and projects forwardly. The result is that it moves up and down alongside the cab or operators position. There has been some demand for avoiding this type of construction in view of the fact that it presents a possibility of accident to the operator. According to the illustrated form of the invention, the boom is located entirely forwardly of the operator.

This forward location of the boom necessitates reducing its length and the length reduction necessitates increasing the angularity of its lifting movement to enable it to lift as high. The boom cannot be kept the same length and project further forward because an attempt to lift a heavy load at a further forward position would unbalance the vehicle and cause a raising of the rear wheels instead of the load. Extending the front wheels further forwardly would be undesirable because that would reduce the maneuverability of the vehicle. It would also reduce the operators visibility, as would mov-. ing the operator further back.

One of the chief objections to a shortened boom is the rapid change of angularity which results. This is particularly objectionable when it produces a change in angularity of the fork 26 or other device supporting the load. Some types of load such as piles of lumber, will not stand much tilting.

Performing hydraulic functions one at a time Although Patent No. 2,788,139 provided a hydraulic cylinder for changing the angularity between the boom ,by providing a self-leveling feature.

3 and the load, it is not practicable to change this angularity during the raising of the boom. In fact, it is highly desirable that no two hydraulic functions be performed at the same time. One reason for this is that sometimes it is desirable for reasons of economy to avoidhaving a separate source of hydraulic pressure for each function, and with a single source the performance of more than one hydraulic function at a time invites trouble. For example, if the valves are open tosimultaneously connect a single hydraulic source to both cylinders 17 and 19, the hydraulic fluid will naturally choose the cylinder having the lowest pressure. In fact, it is even possible for the weight of the load carried by the boom 13 to be so great that the pressure in cylinder 17.wi1l be so high that fluid will actually flow up from cylinder 17 into cylinder 19, allowing the load to descend.

Even when economy does not exclude separate pumps, which would operate two sets of cylinders at the same time, by separately controlled valves, any necessity for doing so would be undesirable from the operators standpoint. It should be realized that the operator often has one hand occupied with steering. Accordingly, it is desirable for him to control the load-handling apparatus with one hand. It is therefore desirable that the equipment be of such nature that it is never necessary for him to operate more than one valve at a time for controlling V the load handling apparatus.

Self-leveling feature The short boom with its rapidly changing angularity is made unobjectionable according to the present invention This self-leveling feature has been worked out so that it functions satisfac torilyin spite of the reaching action previously discussed.

The load-carrying assembly 14 is pivoted to the boom 13 at 31. While other parts remain stationary,-itmay be pivoted through a wide variety of angles with respect to the boom by hydraulic cylinder 32. Hydraulic cylinder 32 and its piston are pivoted to the load-carrying assembly 13 at 33 and to link 34 at 36. Cylinder 32 is double acting, as are all of the other cylinders described. Each control valve has a locking position shutting off all flow of hydraulic fluid to or from either end of the controlled cylinder.

When the cylinder 32 is locked in one position, it functions as one member of the self-leveling linkage. The other members are link 34 pivoted to the boom 13 at 37, link 38pivoted to link 34 and to a forward arm of bell crank lever 39, and link 41, pivoted to the other arm of bell crank lever 39, and to the frame 11. Bell crank lever 39 is pivoted about axis'24, which is the pivotal axis between link 16 and boom 13. V

As seen from FIGURE 5, there is a self-leveling linkage as described above on both sides of the boom 13, namely, on both boom members marked 13 in FIG. 5.

Comparing FIGURES 2 and 4, it will be apparent that as the boom is lowered from the FIGURE 2 position tothe FIGURE 4 position, bell crank lever 39 remains stationary and therefore link 38 causes link 34 to shift angularly with respect to boom 13 so that it draws back on the pivotal point 33 to keep the fork 26in the same angular position with respect to the ground, and with respect to the frame 11. In other words, if the fork 26 is horizontal at the start, it is retained horizontal during the lifting and lowering of boom 13.

Comparing FIGURES l and 4, it is seen that as the boom is retained at one elevation but is retracted or advanced to reach, the bell crank lever 39 retains its angularity with respect to boom 13, although changing its angularity with respect to link 16. In short, the link 41 holds the bell crank lever 39 in the same angular position in spite of movement of the link 16. As a matter of fact, it will be observed from FIGURES l to 4 that the bell crank lever 39 is always in the same position, namely,

l carried by links 38.

4 V with its forward arm vertically disposed, assuming the vehicle is on a level stretch of ground.

Ideally, the linkage forms three coupled parallelograms. The first has its corners at axes 23, 24, 51 and 52. The second has its corners at axes 24, 53, 54 and 37. The: third has its axes at 37, 31, 33 and 36. Of course, for! the latter to be a parallelogram at the right time, the designers must so depose axes 36, 37, 31 and 33 that the plane of the first two will be parallel to the plane of the second two when fork 26 is horizontal. The spacing of axes 36 and 37 must equal that of axes 31 and 33. Then it is inevitable that when the operator operates cylinders 32 to make fork 26 horizontal, he will thereby make the cylinder 32 side of the parallelogram equal to the opposite side. Of course, it is possible that some special considerations may require a departure from the foregoing ideal arrangement of three coupled parallelograms.

It may be observed that the second and third parallelograms function jointly as one parallelogram or pantograph type of linkage with the full length of the boom 13 considered as one of its members.

Transport socket If a load needs to becarried any substantial distance, it is desirable to have the boom come to rest on the chassis independently of the hydraulic cylinders. According to La Tendresses Patent Number 2,788,139, the retracted boom could be lowered to a position at which it would be supported by a fixed member on the chassis. If the boom were advanced beyond the rest position, it could be lowered to' a lower level so as to cause the fork or the load engaging device to reach down to ground level or even lower.

According to the present invention, even greater stability of transportation is provided. Socket 61 is carried by the chassis at a position to receive a dog 62 carried by the boom assembly. In the illustrated form, the dog is As previously indicated, as seen from FIGURE 5, there are two links 38. Hence, there should be two sockets 61 and two dogs 62, one dog on each link 38. 7

To the rear of dog 62 and upwardly therefrom, there is provided a cam surface63 so that if the lowered boom is retracted, it will tend to slide upward, along the cam surface 63 to a position at which the dog 62 can drop into socket 61. V

A side guide 64 is provided along each side of the boom as it is lowered to protect the boom against side swaying. The upper end portions 56 of these side guides are beveled outwardly so as to guide the boom toward center position if it descends while laterally displaced. The side guides 64 help guide the dogs 62 into sockets '61, and also prevent excessive side swaying even if the boom is too high for the dog 62 to rest in socket 61.

For certain types of heavy duty, it is preferred that the two lifting cylinders 17 be provided with separate but jointly controlled hydraulic systems. Thus, there would be two separate hydraulic pumps, jointly driven, two separate valves jointly controlled, and connections from each valve to one of the cylinder lifts 17. Because the pumps are positive displacement pumps of equal output, connecting each such pump to one of the cylinders through valves with the valves operated jointly so as to be equally open, relatively equal movement of the two sides of boom 13 is virtually ensured. The separate revolving of the two lift cylinders, whether supplied by one or two pumps, has the advantage of locking the two cylinders 17 independently. There is no danger, while thus locked, that an oif-center load will drive one boom 13 down enough further than the other to cause operating difliculty or permanent distortion.

- It may be observed that even though a shock-absorbing device 69 is connected to the hydraulic line at the lower end of the lift cylinders 17 as shown, the excessive distortion is satisfactorily avoided by the locking action and relatively equalized lifting action just described.

I claim:

1. Load handling apparatus including a main frame and a link pivoted thereto near the bottom of the link, a boom extending forwardly from the link and pivoted to the link near the top of the link, a load carrying device carried by the boom near the front of the boom and pivoted thereto, means for raising and lowering the boom extending between the boom and the main frame and in at least one boom position being generally parallel to but spaced from the link, and means for pivoting the link about its pivotal connection to the frame, characterized by the provision of linkage for pivoting the load carrying device on the boom approximately inversely and equal to and directly in response to changes in the angularity of the boom to the frame, whereby the load carrying device is maintained at a given relationship with respect to the horizontal in spite of movements of the boom and movements of the link; said linkage including a first pantograph type of linkage including the link as one element and a second pantograph type of linkage including the boom as one element, with a common element coupling the two linkages and providing in the first linkage two parallel pivotal axes spaced along a plane generally parallel to a plane common to axes by which said first linkage is pivoted to the frame, and providing in the second linkage two parallel pivotal axes spaced along a plane generally parallel to a plane common to axes by which the second linkage is pivoted to the load carrying device.

2. Load handling apparatus including a main frame and a link pivoted thereto near the bottom of the link, a boom extending forwardly from the link and pivoted to the link near the top of the link, a load carrying device carried by the boom near the front of the boom and pivoted thereto, means for raising and lowering the boom extending between the boom and the main frame and in at least one boom position being generally parallel to but spaced from the link, and means for pivoting the link about its pivotal connection to the frame, characterized by the provision of linkage for pivoting the load carrying device on the boom approximately inversely and equal to and directly in response to changes in the angularity of the boom to the frame, whereby the load carrying device is maintained at a given relationship with respect to the horizontal in spite of movements of the boom and movements of the link; power means forming part of said linkage for changing the slope of the load carrying device in varying positions of the boom; said linkage including a first pantograph type of linkage including the link as one element and a second pantograph type of linkage including the boom as one element, with a common element coupling the two linkages and providing in the first linkage two parallel pivotal axes spaced along a plane generally parallel to a plane common to axes by which said first linkage is pivoted to the frame, and providing in the second linkage two parallel pivotal axes spaced along a plane generally parallel to a plane common to axes by which the second linkage is pivoted to the load carrying device.

References Cited in the file of this patent UNITED STATES PATENTS 521,256 Browne June 12, 1894 2,348,899 Guignard May 16, 1944 2,500,815 Gerli et a1. Mar. 4, 1950 2,674,500 Hukari Apr. 6, 1954 2,788,139 La Tendresse Apr. 9, 1957 2,817,448 Pilch Dec. 24, 1957 2,820,555 Lessmann Jan. 21, 1958 

